San Francisco’s Board of Supervisors voted 10-1 to ban the use of non-biodegradable plastic bags; supermarkets across the city will retrain their employees to ask: paper or biodegradable plastic?

The Plastic Bag Reduction Ordinance, written by Supervisor Ross Mirkarimi and Co., sponsored by six other supervisors, gives major supermarket chains with more than $2 million in annual sales six months to make the switch to biodegradable bags. Pharmacies and retailers with at least five locations have one year. Violators face fines of up to $500.

Supermarkets have let economics guide their choice between paper and plastic. Paper bags cost four cents, while plastic bags cost a penny. The largest San Francisco supermarket hands out 125 million plastic bags each year.